1. Field of the Invention
The present invention relates to a portable terminal device incorporating a function of automatically controlling a transmitting voice level and a calling sound level.
2. Description of the Related Art
There has hitherto been proposed a portable mobile telephone contrived to detect an ambient noise level and to control a level of a receiving voice from a loudspeaker in accordance with the detected noise level.
FIG. 1 is a block diagram illustrating a portable mobile telephone. Referring to FIG. 1, a noise level detection control circuit 43 detects a level of noise ambient to a user, which is contained in a signal component inputted from a microphone 48. Then, a loudspeaker drive amplifier 44 is controlled corresponding to the thus detected ambient noise level, thus increasing and decreasing a voice level outputted from a loudspeaker 47. More specifically, the noise level detection control circuit 43 increases the voice level outputted from the loudspeaker 47 when the ambient noise level rises, and decreases the voice level outputted from the loudspeaker 47 when the ambient noise level decreases, thereby eliminating an influence of the ambient noises upon the receiving voice level.
On the other hand, in this portable mobile telephone, a voice level detection control circuit 46 judges whether or not a voice of the user is inputted from the microphone 48, and controls a gain of an output signal of the microphone 48 based on a result of this judgement. To be more specific, the gain of the output signal of the microphone 48 is decreased if the voice of the user is not inputted but is increased if inputted, thereby controlling so as not to increase the gain with respect to the noise component in the case of the voice not being inputted.
This type of portable mobile telephone is disclosed in, e.g., Japanese laid-open patent application heisei 2-117228.
This type of portable mobile telephone, however, involves the use of a noise level detection circuit for controlling the receiving voice level and a voice level detection circuit for controlling the transmitting voice level.